1. Field of the Invention
This invention relates to fluidic devices and, more particularly, to fluidic apparatus which provides a direct measure of the partial pressure of a gas constituent in a mixture relative to a reference gas.
2. Description of the Prior Art
In an oxygen control system for aircraft pilots, it becomes necessary to control the oxygen delivery to the pilot as a function of altitude. That is, it is preferable to be able to provide the ground equivalent of oxygen to the pilot of an aircraft regardless of the altitude. In a physical sense, this requirement may be stated as that of providing a constant partial pressure of oxygen.
Prior art techniques utilized to control the amount of oxygen delivered to the pilot of an aircraft utilize concentration sensors which schedule the concentration of oxygen to be delivered as a function of the altitude of the aircraft. Such devices require a pair of measurements, i.e., concentration and altitude, and various computation equipment in order to schedule the right amount of oxygen to be admixed to the ambient air. Further, such devices are not generally responsive to situations involving varying ambient pressures.
It is therefore realized that it would be extremely advantageous to provide a device by means of which the partial pressure of a constituent gas within a mixture could be measured directly relative to a reference gas without the necessity for having an intermediate measurement of either concentration thereof or the altitude of the aircraft, or both.
Prior art United States patents in this field of which I am aware including the following U.S. Pat. Nos.: 2,283,750; 2,630,129; 2,998,009; 3,468,157; 3,556,098; 3,722,510; and 3,817,085. However, none of the foregoing patents provide a solution which approaches the simplicity, ruggedness, accuracy and versatility of the present invention to be described in more detail hereinafter.